2 * Detect hard and soft lockups on a system
4 * started by Don Zickus, Copyright (C) 2010 Red Hat, Inc.
6 * Note: Most of this code is borrowed heavily from the original softlockup
7 * detector, so thanks to Ingo for the initial implementation.
8 * Some chunks also taken from the old x86-specific nmi watchdog code, thanks
9 * to those contributors as well.
12 #define pr_fmt(fmt) "NMI watchdog: " fmt
15 #include <linux/cpu.h>
16 #include <linux/nmi.h>
17 #include <linux/init.h>
18 #include <linux/module.h>
19 #include <linux/sysctl.h>
20 #include <linux/smpboot.h>
21 #include <linux/sched/rt.h>
22 #include <linux/tick.h>
23 #include <linux/workqueue.h>
25 #include <asm/irq_regs.h>
26 #include <linux/kvm_para.h>
27 #include <linux/perf_event.h>
28 #include <linux/kthread.h>
31 * The run state of the lockup detectors is controlled by the content of the
32 * 'watchdog_enabled' variable. Each lockup detector has its dedicated bit -
33 * bit 0 for the hard lockup detector and bit 1 for the soft lockup detector.
35 * 'watchdog_user_enabled', 'nmi_watchdog_enabled' and 'soft_watchdog_enabled'
36 * are variables that are only used as an 'interface' between the parameters
37 * in /proc/sys/kernel and the internal state bits in 'watchdog_enabled'. The
38 * 'watchdog_thresh' variable is handled differently because its value is not
39 * boolean, and the lockup detectors are 'suspended' while 'watchdog_thresh'
42 #define NMI_WATCHDOG_ENABLED_BIT 0
43 #define SOFT_WATCHDOG_ENABLED_BIT 1
44 #define NMI_WATCHDOG_ENABLED (1 << NMI_WATCHDOG_ENABLED_BIT)
45 #define SOFT_WATCHDOG_ENABLED (1 << SOFT_WATCHDOG_ENABLED_BIT)
47 static DEFINE_MUTEX(watchdog_proc_mutex
);
49 #ifdef CONFIG_HARDLOCKUP_DETECTOR
50 static unsigned long __read_mostly watchdog_enabled
= SOFT_WATCHDOG_ENABLED
|NMI_WATCHDOG_ENABLED
;
52 static unsigned long __read_mostly watchdog_enabled
= SOFT_WATCHDOG_ENABLED
;
54 int __read_mostly nmi_watchdog_enabled
;
55 int __read_mostly soft_watchdog_enabled
;
56 int __read_mostly watchdog_user_enabled
;
57 int __read_mostly watchdog_thresh
= 10;
60 int __read_mostly sysctl_softlockup_all_cpu_backtrace
;
61 int __read_mostly sysctl_hardlockup_all_cpu_backtrace
;
63 #define sysctl_softlockup_all_cpu_backtrace 0
64 #define sysctl_hardlockup_all_cpu_backtrace 0
66 static struct cpumask watchdog_cpumask __read_mostly
;
67 unsigned long *watchdog_cpumask_bits
= cpumask_bits(&watchdog_cpumask
);
69 /* Helper for online, unparked cpus. */
70 #define for_each_watchdog_cpu(cpu) \
71 for_each_cpu_and((cpu), cpu_online_mask, &watchdog_cpumask)
74 * The 'watchdog_running' variable is set to 1 when the watchdog threads
75 * are registered/started and is set to 0 when the watchdog threads are
76 * unregistered/stopped, so it is an indicator whether the threads exist.
78 static int __read_mostly watchdog_running
;
80 * If a subsystem has a need to deactivate the watchdog temporarily, it
81 * can use the suspend/resume interface to achieve this. The content of
82 * the 'watchdog_suspended' variable reflects this state. Existing threads
83 * are parked/unparked by the lockup_detector_{suspend|resume} functions
84 * (see comment blocks pertaining to those functions for further details).
86 * 'watchdog_suspended' also prevents threads from being registered/started
87 * or unregistered/stopped via parameters in /proc/sys/kernel, so the state
88 * of 'watchdog_running' cannot change while the watchdog is deactivated
89 * temporarily (see related code in 'proc' handlers).
91 static int __read_mostly watchdog_suspended
;
93 static u64 __read_mostly sample_period
;
95 static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts
);
96 static DEFINE_PER_CPU(struct task_struct
*, softlockup_watchdog
);
97 static DEFINE_PER_CPU(struct hrtimer
, watchdog_hrtimer
);
98 static DEFINE_PER_CPU(bool, softlockup_touch_sync
);
99 static DEFINE_PER_CPU(bool, soft_watchdog_warn
);
100 static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts
);
101 static DEFINE_PER_CPU(unsigned long, soft_lockup_hrtimer_cnt
);
102 static DEFINE_PER_CPU(struct task_struct
*, softlockup_task_ptr_saved
);
103 #ifdef CONFIG_HARDLOCKUP_DETECTOR
104 static DEFINE_PER_CPU(bool, hard_watchdog_warn
);
105 static DEFINE_PER_CPU(bool, watchdog_nmi_touch
);
106 static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts_saved
);
107 static DEFINE_PER_CPU(struct perf_event
*, watchdog_ev
);
109 static unsigned long soft_lockup_nmi_warn
;
113 * Should we panic when a soft-lockup or hard-lockup occurs:
115 #ifdef CONFIG_HARDLOCKUP_DETECTOR
116 unsigned int __read_mostly hardlockup_panic
=
117 CONFIG_BOOTPARAM_HARDLOCKUP_PANIC_VALUE
;
118 static unsigned long hardlockup_allcpu_dumped
;
120 * We may not want to enable hard lockup detection by default in all cases,
121 * for example when running the kernel as a guest on a hypervisor. In these
122 * cases this function can be called to disable hard lockup detection. This
123 * function should only be executed once by the boot processor before the
124 * kernel command line parameters are parsed, because otherwise it is not
125 * possible to override this in hardlockup_panic_setup().
127 void hardlockup_detector_disable(void)
129 watchdog_enabled
&= ~NMI_WATCHDOG_ENABLED
;
132 static int __init
hardlockup_panic_setup(char *str
)
134 if (!strncmp(str
, "panic", 5))
135 hardlockup_panic
= 1;
136 else if (!strncmp(str
, "nopanic", 7))
137 hardlockup_panic
= 0;
138 else if (!strncmp(str
, "0", 1))
139 watchdog_enabled
&= ~NMI_WATCHDOG_ENABLED
;
140 else if (!strncmp(str
, "1", 1))
141 watchdog_enabled
|= NMI_WATCHDOG_ENABLED
;
144 __setup("nmi_watchdog=", hardlockup_panic_setup
);
147 unsigned int __read_mostly softlockup_panic
=
148 CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC_VALUE
;
150 static int __init
softlockup_panic_setup(char *str
)
152 softlockup_panic
= simple_strtoul(str
, NULL
, 0);
156 __setup("softlockup_panic=", softlockup_panic_setup
);
158 static int __init
nowatchdog_setup(char *str
)
160 watchdog_enabled
= 0;
163 __setup("nowatchdog", nowatchdog_setup
);
165 static int __init
nosoftlockup_setup(char *str
)
167 watchdog_enabled
&= ~SOFT_WATCHDOG_ENABLED
;
170 __setup("nosoftlockup", nosoftlockup_setup
);
173 static int __init
softlockup_all_cpu_backtrace_setup(char *str
)
175 sysctl_softlockup_all_cpu_backtrace
=
176 !!simple_strtol(str
, NULL
, 0);
179 __setup("softlockup_all_cpu_backtrace=", softlockup_all_cpu_backtrace_setup
);
180 static int __init
hardlockup_all_cpu_backtrace_setup(char *str
)
182 sysctl_hardlockup_all_cpu_backtrace
=
183 !!simple_strtol(str
, NULL
, 0);
186 __setup("hardlockup_all_cpu_backtrace=", hardlockup_all_cpu_backtrace_setup
);
190 * Hard-lockup warnings should be triggered after just a few seconds. Soft-
191 * lockups can have false positives under extreme conditions. So we generally
192 * want a higher threshold for soft lockups than for hard lockups. So we couple
193 * the thresholds with a factor: we make the soft threshold twice the amount of
194 * time the hard threshold is.
196 static int get_softlockup_thresh(void)
198 return watchdog_thresh
* 2;
202 * Returns seconds, approximately. We don't need nanosecond
203 * resolution, and we don't need to waste time with a big divide when
206 static unsigned long get_timestamp(void)
208 return running_clock() >> 30LL; /* 2^30 ~= 10^9 */
211 static void set_sample_period(void)
214 * convert watchdog_thresh from seconds to ns
215 * the divide by 5 is to give hrtimer several chances (two
216 * or three with the current relation between the soft
217 * and hard thresholds) to increment before the
218 * hardlockup detector generates a warning
220 sample_period
= get_softlockup_thresh() * ((u64
)NSEC_PER_SEC
/ 5);
223 /* Commands for resetting the watchdog */
224 static void __touch_watchdog(void)
226 __this_cpu_write(watchdog_touch_ts
, get_timestamp());
230 * touch_softlockup_watchdog_sched - touch watchdog on scheduler stalls
232 * Call when the scheduler may have stalled for legitimate reasons
233 * preventing the watchdog task from executing - e.g. the scheduler
234 * entering idle state. This should only be used for scheduler events.
235 * Use touch_softlockup_watchdog() for everything else.
237 void touch_softlockup_watchdog_sched(void)
240 * Preemption can be enabled. It doesn't matter which CPU's timestamp
241 * gets zeroed here, so use the raw_ operation.
243 raw_cpu_write(watchdog_touch_ts
, 0);
246 void touch_softlockup_watchdog(void)
248 touch_softlockup_watchdog_sched();
249 wq_watchdog_touch(raw_smp_processor_id());
251 EXPORT_SYMBOL(touch_softlockup_watchdog
);
253 void touch_all_softlockup_watchdogs(void)
258 * this is done lockless
259 * do we care if a 0 races with a timestamp?
260 * all it means is the softlock check starts one cycle later
262 for_each_watchdog_cpu(cpu
)
263 per_cpu(watchdog_touch_ts
, cpu
) = 0;
264 wq_watchdog_touch(-1);
267 #ifdef CONFIG_HARDLOCKUP_DETECTOR
268 void touch_nmi_watchdog(void)
271 * Using __raw here because some code paths have
272 * preemption enabled. If preemption is enabled
273 * then interrupts should be enabled too, in which
274 * case we shouldn't have to worry about the watchdog
277 raw_cpu_write(watchdog_nmi_touch
, true);
278 touch_softlockup_watchdog();
280 EXPORT_SYMBOL(touch_nmi_watchdog
);
284 void touch_softlockup_watchdog_sync(void)
286 __this_cpu_write(softlockup_touch_sync
, true);
287 __this_cpu_write(watchdog_touch_ts
, 0);
290 #ifdef CONFIG_HARDLOCKUP_DETECTOR
291 /* watchdog detector functions */
292 static bool is_hardlockup(void)
294 unsigned long hrint
= __this_cpu_read(hrtimer_interrupts
);
296 if (__this_cpu_read(hrtimer_interrupts_saved
) == hrint
)
299 __this_cpu_write(hrtimer_interrupts_saved
, hrint
);
304 static int is_softlockup(unsigned long touch_ts
)
306 unsigned long now
= get_timestamp();
308 if ((watchdog_enabled
& SOFT_WATCHDOG_ENABLED
) && watchdog_thresh
){
309 /* Warn about unreasonable delays. */
310 if (time_after(now
, touch_ts
+ get_softlockup_thresh()))
311 return now
- touch_ts
;
316 #ifdef CONFIG_HARDLOCKUP_DETECTOR
318 static struct perf_event_attr wd_hw_attr
= {
319 .type
= PERF_TYPE_HARDWARE
,
320 .config
= PERF_COUNT_HW_CPU_CYCLES
,
321 .size
= sizeof(struct perf_event_attr
),
326 /* Callback function for perf event subsystem */
327 static void watchdog_overflow_callback(struct perf_event
*event
,
328 struct perf_sample_data
*data
,
329 struct pt_regs
*regs
)
331 /* Ensure the watchdog never gets throttled */
332 event
->hw
.interrupts
= 0;
334 if (__this_cpu_read(watchdog_nmi_touch
) == true) {
335 __this_cpu_write(watchdog_nmi_touch
, false);
339 /* check for a hardlockup
340 * This is done by making sure our timer interrupt
341 * is incrementing. The timer interrupt should have
342 * fired multiple times before we overflow'd. If it hasn't
343 * then this is a good indication the cpu is stuck
345 if (is_hardlockup()) {
346 int this_cpu
= smp_processor_id();
348 /* only print hardlockups once */
349 if (__this_cpu_read(hard_watchdog_warn
) == true)
352 pr_emerg("Watchdog detected hard LOCKUP on cpu %d", this_cpu
);
354 print_irqtrace_events(current
);
361 * Perform all-CPU dump only once to avoid multiple hardlockups
362 * generating interleaving traces
364 if (sysctl_hardlockup_all_cpu_backtrace
&&
365 !test_and_set_bit(0, &hardlockup_allcpu_dumped
))
366 trigger_allbutself_cpu_backtrace();
368 if (hardlockup_panic
)
369 nmi_panic(regs
, "Hard LOCKUP");
371 __this_cpu_write(hard_watchdog_warn
, true);
375 __this_cpu_write(hard_watchdog_warn
, false);
378 #endif /* CONFIG_HARDLOCKUP_DETECTOR */
380 static void watchdog_interrupt_count(void)
382 __this_cpu_inc(hrtimer_interrupts
);
385 static int watchdog_nmi_enable(unsigned int cpu
);
386 static void watchdog_nmi_disable(unsigned int cpu
);
388 static int watchdog_enable_all_cpus(void);
389 static void watchdog_disable_all_cpus(void);
391 /* watchdog kicker functions */
392 static enum hrtimer_restart
watchdog_timer_fn(struct hrtimer
*hrtimer
)
394 unsigned long touch_ts
= __this_cpu_read(watchdog_touch_ts
);
395 struct pt_regs
*regs
= get_irq_regs();
397 int softlockup_all_cpu_backtrace
= sysctl_softlockup_all_cpu_backtrace
;
399 /* kick the hardlockup detector */
400 watchdog_interrupt_count();
402 /* kick the softlockup detector */
403 wake_up_process(__this_cpu_read(softlockup_watchdog
));
406 hrtimer_forward_now(hrtimer
, ns_to_ktime(sample_period
));
409 if (unlikely(__this_cpu_read(softlockup_touch_sync
))) {
411 * If the time stamp was touched atomically
412 * make sure the scheduler tick is up to date.
414 __this_cpu_write(softlockup_touch_sync
, false);
418 /* Clear the guest paused flag on watchdog reset */
419 kvm_check_and_clear_guest_paused();
421 return HRTIMER_RESTART
;
424 /* check for a softlockup
425 * This is done by making sure a high priority task is
426 * being scheduled. The task touches the watchdog to
427 * indicate it is getting cpu time. If it hasn't then
428 * this is a good indication some task is hogging the cpu
430 duration
= is_softlockup(touch_ts
);
431 if (unlikely(duration
)) {
433 * If a virtual machine is stopped by the host it can look to
434 * the watchdog like a soft lockup, check to see if the host
435 * stopped the vm before we issue the warning
437 if (kvm_check_and_clear_guest_paused())
438 return HRTIMER_RESTART
;
441 if (__this_cpu_read(soft_watchdog_warn
) == true) {
443 * When multiple processes are causing softlockups the
444 * softlockup detector only warns on the first one
445 * because the code relies on a full quiet cycle to
446 * re-arm. The second process prevents the quiet cycle
447 * and never gets reported. Use task pointers to detect
450 if (__this_cpu_read(softlockup_task_ptr_saved
) !=
452 __this_cpu_write(soft_watchdog_warn
, false);
455 return HRTIMER_RESTART
;
458 if (softlockup_all_cpu_backtrace
) {
459 /* Prevent multiple soft-lockup reports if one cpu is already
460 * engaged in dumping cpu back traces
462 if (test_and_set_bit(0, &soft_lockup_nmi_warn
)) {
463 /* Someone else will report us. Let's give up */
464 __this_cpu_write(soft_watchdog_warn
, true);
465 return HRTIMER_RESTART
;
469 pr_emerg("BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n",
470 smp_processor_id(), duration
,
471 current
->comm
, task_pid_nr(current
));
472 __this_cpu_write(softlockup_task_ptr_saved
, current
);
474 print_irqtrace_events(current
);
480 if (softlockup_all_cpu_backtrace
) {
481 /* Avoid generating two back traces for current
482 * given that one is already made above
484 trigger_allbutself_cpu_backtrace();
486 clear_bit(0, &soft_lockup_nmi_warn
);
487 /* Barrier to sync with other cpus */
488 smp_mb__after_atomic();
491 add_taint(TAINT_SOFTLOCKUP
, LOCKDEP_STILL_OK
);
492 if (softlockup_panic
)
493 panic("softlockup: hung tasks");
494 __this_cpu_write(soft_watchdog_warn
, true);
496 __this_cpu_write(soft_watchdog_warn
, false);
498 return HRTIMER_RESTART
;
501 static void watchdog_set_prio(unsigned int policy
, unsigned int prio
)
503 struct sched_param param
= { .sched_priority
= prio
};
505 sched_setscheduler(current
, policy
, ¶m
);
508 static void watchdog_enable(unsigned int cpu
)
510 struct hrtimer
*hrtimer
= raw_cpu_ptr(&watchdog_hrtimer
);
512 /* kick off the timer for the hardlockup detector */
513 hrtimer_init(hrtimer
, CLOCK_MONOTONIC
, HRTIMER_MODE_REL
);
514 hrtimer
->function
= watchdog_timer_fn
;
516 /* Enable the perf event */
517 watchdog_nmi_enable(cpu
);
519 /* done here because hrtimer_start can only pin to smp_processor_id() */
520 hrtimer_start(hrtimer
, ns_to_ktime(sample_period
),
521 HRTIMER_MODE_REL_PINNED
);
523 /* initialize timestamp */
524 watchdog_set_prio(SCHED_FIFO
, MAX_RT_PRIO
- 1);
528 static void watchdog_disable(unsigned int cpu
)
530 struct hrtimer
*hrtimer
= raw_cpu_ptr(&watchdog_hrtimer
);
532 watchdog_set_prio(SCHED_NORMAL
, 0);
533 hrtimer_cancel(hrtimer
);
534 /* disable the perf event */
535 watchdog_nmi_disable(cpu
);
538 static void watchdog_cleanup(unsigned int cpu
, bool online
)
540 watchdog_disable(cpu
);
543 static int watchdog_should_run(unsigned int cpu
)
545 return __this_cpu_read(hrtimer_interrupts
) !=
546 __this_cpu_read(soft_lockup_hrtimer_cnt
);
550 * The watchdog thread function - touches the timestamp.
552 * It only runs once every sample_period seconds (4 seconds by
553 * default) to reset the softlockup timestamp. If this gets delayed
554 * for more than 2*watchdog_thresh seconds then the debug-printout
555 * triggers in watchdog_timer_fn().
557 static void watchdog(unsigned int cpu
)
559 __this_cpu_write(soft_lockup_hrtimer_cnt
,
560 __this_cpu_read(hrtimer_interrupts
));
564 * watchdog_nmi_enable() clears the NMI_WATCHDOG_ENABLED bit in the
565 * failure path. Check for failures that can occur asynchronously -
566 * for example, when CPUs are on-lined - and shut down the hardware
567 * perf event on each CPU accordingly.
569 * The only non-obvious place this bit can be cleared is through
570 * watchdog_nmi_enable(), so a pr_info() is placed there. Placing a
571 * pr_info here would be too noisy as it would result in a message
572 * every few seconds if the hardlockup was disabled but the softlockup
575 if (!(watchdog_enabled
& NMI_WATCHDOG_ENABLED
))
576 watchdog_nmi_disable(cpu
);
579 #ifdef CONFIG_HARDLOCKUP_DETECTOR
581 * People like the simple clean cpu node info on boot.
582 * Reduce the watchdog noise by only printing messages
583 * that are different from what cpu0 displayed.
585 static unsigned long cpu0_err
;
587 static int watchdog_nmi_enable(unsigned int cpu
)
589 struct perf_event_attr
*wd_attr
;
590 struct perf_event
*event
= per_cpu(watchdog_ev
, cpu
);
592 /* nothing to do if the hard lockup detector is disabled */
593 if (!(watchdog_enabled
& NMI_WATCHDOG_ENABLED
))
596 /* is it already setup and enabled? */
597 if (event
&& event
->state
> PERF_EVENT_STATE_OFF
)
600 /* it is setup but not enabled */
604 wd_attr
= &wd_hw_attr
;
605 wd_attr
->sample_period
= hw_nmi_get_sample_period(watchdog_thresh
);
607 /* Try to register using hardware perf events */
608 event
= perf_event_create_kernel_counter(wd_attr
, cpu
, NULL
, watchdog_overflow_callback
, NULL
);
610 /* save cpu0 error for future comparision */
611 if (cpu
== 0 && IS_ERR(event
))
612 cpu0_err
= PTR_ERR(event
);
614 if (!IS_ERR(event
)) {
615 /* only print for cpu0 or different than cpu0 */
616 if (cpu
== 0 || cpu0_err
)
617 pr_info("enabled on all CPUs, permanently consumes one hw-PMU counter.\n");
622 * Disable the hard lockup detector if _any_ CPU fails to set up
623 * set up the hardware perf event. The watchdog() function checks
624 * the NMI_WATCHDOG_ENABLED bit periodically.
626 * The barriers are for syncing up watchdog_enabled across all the
627 * cpus, as clear_bit() does not use barriers.
629 smp_mb__before_atomic();
630 clear_bit(NMI_WATCHDOG_ENABLED_BIT
, &watchdog_enabled
);
631 smp_mb__after_atomic();
633 /* skip displaying the same error again */
634 if (cpu
> 0 && (PTR_ERR(event
) == cpu0_err
))
635 return PTR_ERR(event
);
637 /* vary the KERN level based on the returned errno */
638 if (PTR_ERR(event
) == -EOPNOTSUPP
)
639 pr_info("disabled (cpu%i): not supported (no LAPIC?)\n", cpu
);
640 else if (PTR_ERR(event
) == -ENOENT
)
641 pr_warn("disabled (cpu%i): hardware events not enabled\n",
644 pr_err("disabled (cpu%i): unable to create perf event: %ld\n",
645 cpu
, PTR_ERR(event
));
647 pr_info("Shutting down hard lockup detector on all cpus\n");
649 return PTR_ERR(event
);
653 per_cpu(watchdog_ev
, cpu
) = event
;
655 perf_event_enable(per_cpu(watchdog_ev
, cpu
));
660 static void watchdog_nmi_disable(unsigned int cpu
)
662 struct perf_event
*event
= per_cpu(watchdog_ev
, cpu
);
665 perf_event_disable(event
);
666 per_cpu(watchdog_ev
, cpu
) = NULL
;
668 /* should be in cleanup, but blocks oprofile */
669 perf_event_release_kernel(event
);
672 /* watchdog_nmi_enable() expects this to be zero initially. */
678 static int watchdog_nmi_enable(unsigned int cpu
) { return 0; }
679 static void watchdog_nmi_disable(unsigned int cpu
) { return; }
680 #endif /* CONFIG_HARDLOCKUP_DETECTOR */
682 static struct smp_hotplug_thread watchdog_threads
= {
683 .store
= &softlockup_watchdog
,
684 .thread_should_run
= watchdog_should_run
,
685 .thread_fn
= watchdog
,
686 .thread_comm
= "watchdog/%u",
687 .setup
= watchdog_enable
,
688 .cleanup
= watchdog_cleanup
,
689 .park
= watchdog_disable
,
690 .unpark
= watchdog_enable
,
694 * park all watchdog threads that are specified in 'watchdog_cpumask'
696 * This function returns an error if kthread_park() of a watchdog thread
697 * fails. In this situation, the watchdog threads of some CPUs can already
698 * be parked and the watchdog threads of other CPUs can still be runnable.
699 * Callers are expected to handle this special condition as appropriate in
702 * This function may only be called in a context that is protected against
703 * races with CPU hotplug - for example, via get_online_cpus().
705 static int watchdog_park_threads(void)
709 for_each_watchdog_cpu(cpu
) {
710 ret
= kthread_park(per_cpu(softlockup_watchdog
, cpu
));
719 * unpark all watchdog threads that are specified in 'watchdog_cpumask'
721 * This function may only be called in a context that is protected against
722 * races with CPU hotplug - for example, via get_online_cpus().
724 static void watchdog_unpark_threads(void)
728 for_each_watchdog_cpu(cpu
)
729 kthread_unpark(per_cpu(softlockup_watchdog
, cpu
));
733 * Suspend the hard and soft lockup detector by parking the watchdog threads.
735 int lockup_detector_suspend(void)
740 mutex_lock(&watchdog_proc_mutex
);
742 * Multiple suspend requests can be active in parallel (counted by
743 * the 'watchdog_suspended' variable). If the watchdog threads are
744 * running, the first caller takes care that they will be parked.
745 * The state of 'watchdog_running' cannot change while a suspend
746 * request is active (see related code in 'proc' handlers).
748 if (watchdog_running
&& !watchdog_suspended
)
749 ret
= watchdog_park_threads();
752 watchdog_suspended
++;
754 watchdog_disable_all_cpus();
755 pr_err("Failed to suspend lockup detectors, disabled\n");
756 watchdog_enabled
= 0;
759 mutex_unlock(&watchdog_proc_mutex
);
765 * Resume the hard and soft lockup detector by unparking the watchdog threads.
767 void lockup_detector_resume(void)
769 mutex_lock(&watchdog_proc_mutex
);
771 watchdog_suspended
--;
773 * The watchdog threads are unparked if they were previously running
774 * and if there is no more active suspend request.
776 if (watchdog_running
&& !watchdog_suspended
)
777 watchdog_unpark_threads();
779 mutex_unlock(&watchdog_proc_mutex
);
783 static int update_watchdog_all_cpus(void)
787 ret
= watchdog_park_threads();
791 watchdog_unpark_threads();
796 static int watchdog_enable_all_cpus(void)
800 if (!watchdog_running
) {
801 err
= smpboot_register_percpu_thread_cpumask(&watchdog_threads
,
804 pr_err("Failed to create watchdog threads, disabled\n");
806 watchdog_running
= 1;
809 * Enable/disable the lockup detectors or
810 * change the sample period 'on the fly'.
812 err
= update_watchdog_all_cpus();
815 watchdog_disable_all_cpus();
816 pr_err("Failed to update lockup detectors, disabled\n");
821 watchdog_enabled
= 0;
826 static void watchdog_disable_all_cpus(void)
828 if (watchdog_running
) {
829 watchdog_running
= 0;
830 smpboot_unregister_percpu_thread(&watchdog_threads
);
837 * Update the run state of the lockup detectors.
839 static int proc_watchdog_update(void)
844 * Watchdog threads won't be started if they are already active.
845 * The 'watchdog_running' variable in watchdog_*_all_cpus() takes
846 * care of this. If those threads are already active, the sample
847 * period will be updated and the lockup detectors will be enabled
848 * or disabled 'on the fly'.
850 if (watchdog_enabled
&& watchdog_thresh
)
851 err
= watchdog_enable_all_cpus();
853 watchdog_disable_all_cpus();
860 * common function for watchdog, nmi_watchdog and soft_watchdog parameter
862 * caller | table->data points to | 'which' contains the flag(s)
863 * -------------------|-----------------------|-----------------------------
864 * proc_watchdog | watchdog_user_enabled | NMI_WATCHDOG_ENABLED or'ed
865 * | | with SOFT_WATCHDOG_ENABLED
866 * -------------------|-----------------------|-----------------------------
867 * proc_nmi_watchdog | nmi_watchdog_enabled | NMI_WATCHDOG_ENABLED
868 * -------------------|-----------------------|-----------------------------
869 * proc_soft_watchdog | soft_watchdog_enabled | SOFT_WATCHDOG_ENABLED
871 static int proc_watchdog_common(int which
, struct ctl_table
*table
, int write
,
872 void __user
*buffer
, size_t *lenp
, loff_t
*ppos
)
875 int *watchdog_param
= (int *)table
->data
;
878 mutex_lock(&watchdog_proc_mutex
);
880 if (watchdog_suspended
) {
881 /* no parameter changes allowed while watchdog is suspended */
887 * If the parameter is being read return the state of the corresponding
888 * bit(s) in 'watchdog_enabled', else update 'watchdog_enabled' and the
889 * run state of the lockup detectors.
892 *watchdog_param
= (watchdog_enabled
& which
) != 0;
893 err
= proc_dointvec_minmax(table
, write
, buffer
, lenp
, ppos
);
895 err
= proc_dointvec_minmax(table
, write
, buffer
, lenp
, ppos
);
900 * There is a race window between fetching the current value
901 * from 'watchdog_enabled' and storing the new value. During
902 * this race window, watchdog_nmi_enable() can sneak in and
903 * clear the NMI_WATCHDOG_ENABLED bit in 'watchdog_enabled'.
904 * The 'cmpxchg' detects this race and the loop retries.
907 old
= watchdog_enabled
;
909 * If the parameter value is not zero set the
910 * corresponding bit(s), else clear it(them).
916 } while (cmpxchg(&watchdog_enabled
, old
, new) != old
);
919 * Update the run state of the lockup detectors. There is _no_
920 * need to check the value returned by proc_watchdog_update()
921 * and to restore the previous value of 'watchdog_enabled' as
922 * both lockup detectors are disabled if proc_watchdog_update()
928 err
= proc_watchdog_update();
931 mutex_unlock(&watchdog_proc_mutex
);
937 * /proc/sys/kernel/watchdog
939 int proc_watchdog(struct ctl_table
*table
, int write
,
940 void __user
*buffer
, size_t *lenp
, loff_t
*ppos
)
942 return proc_watchdog_common(NMI_WATCHDOG_ENABLED
|SOFT_WATCHDOG_ENABLED
,
943 table
, write
, buffer
, lenp
, ppos
);
947 * /proc/sys/kernel/nmi_watchdog
949 int proc_nmi_watchdog(struct ctl_table
*table
, int write
,
950 void __user
*buffer
, size_t *lenp
, loff_t
*ppos
)
952 return proc_watchdog_common(NMI_WATCHDOG_ENABLED
,
953 table
, write
, buffer
, lenp
, ppos
);
957 * /proc/sys/kernel/soft_watchdog
959 int proc_soft_watchdog(struct ctl_table
*table
, int write
,
960 void __user
*buffer
, size_t *lenp
, loff_t
*ppos
)
962 return proc_watchdog_common(SOFT_WATCHDOG_ENABLED
,
963 table
, write
, buffer
, lenp
, ppos
);
967 * /proc/sys/kernel/watchdog_thresh
969 int proc_watchdog_thresh(struct ctl_table
*table
, int write
,
970 void __user
*buffer
, size_t *lenp
, loff_t
*ppos
)
975 mutex_lock(&watchdog_proc_mutex
);
977 if (watchdog_suspended
) {
978 /* no parameter changes allowed while watchdog is suspended */
983 old
= ACCESS_ONCE(watchdog_thresh
);
984 err
= proc_dointvec_minmax(table
, write
, buffer
, lenp
, ppos
);
990 * Update the sample period. Restore on failure.
992 new = ACCESS_ONCE(watchdog_thresh
);
997 err
= proc_watchdog_update();
999 watchdog_thresh
= old
;
1000 set_sample_period();
1003 mutex_unlock(&watchdog_proc_mutex
);
1009 * The cpumask is the mask of possible cpus that the watchdog can run
1010 * on, not the mask of cpus it is actually running on. This allows the
1011 * user to specify a mask that will include cpus that have not yet
1012 * been brought online, if desired.
1014 int proc_watchdog_cpumask(struct ctl_table
*table
, int write
,
1015 void __user
*buffer
, size_t *lenp
, loff_t
*ppos
)
1020 mutex_lock(&watchdog_proc_mutex
);
1022 if (watchdog_suspended
) {
1023 /* no parameter changes allowed while watchdog is suspended */
1028 err
= proc_do_large_bitmap(table
, write
, buffer
, lenp
, ppos
);
1029 if (!err
&& write
) {
1030 /* Remove impossible cpus to keep sysctl output cleaner. */
1031 cpumask_and(&watchdog_cpumask
, &watchdog_cpumask
,
1034 if (watchdog_running
) {
1036 * Failure would be due to being unable to allocate
1037 * a temporary cpumask, so we are likely not in a
1038 * position to do much else to make things better.
1040 if (smpboot_update_cpumask_percpu_thread(
1041 &watchdog_threads
, &watchdog_cpumask
) != 0)
1042 pr_err("cpumask update failed\n");
1046 mutex_unlock(&watchdog_proc_mutex
);
1051 #endif /* CONFIG_SYSCTL */
1053 void __init
lockup_detector_init(void)
1055 set_sample_period();
1057 #ifdef CONFIG_NO_HZ_FULL
1058 if (tick_nohz_full_enabled()) {
1059 pr_info("Disabling watchdog on nohz_full cores by default\n");
1060 cpumask_copy(&watchdog_cpumask
, housekeeping_mask
);
1062 cpumask_copy(&watchdog_cpumask
, cpu_possible_mask
);
1064 cpumask_copy(&watchdog_cpumask
, cpu_possible_mask
);
1067 if (watchdog_enabled
)
1068 watchdog_enable_all_cpus();